JP2001073748A - Cleaning and regeneration system and device for particulate filter for diesel engine exhaust gas - Google Patents

Abstract

(57) [Problem] To provide a particulate filter (DPF) regeneration device for diesel engine exhaust gas. In A (1) upstream NO to have the exhaust gas recirculation comprise a _x storage-reduction catalyst (EGR) expression side diesel engine of the DPF along with delaying the timing of the catalyst regeneration, EGR, the intake control valve, exhaust control The NOx storage-reduction catalyst and the DPF can be regenerated by controlling the switching between the lean state and the rich state by applying the injection of the valve and the reducing agent alone or in an appropriate combination. (3) above-mentioned (1)
Using noble metal oxidation catalyst instead of the NO _x storage reduction catalysts in the same device as used, without the reducing agent injection, EGR, control the exhaust gas temperature by suitably combining application of intake / exhaust control; (4) The same effect is obtained by omitting the noble metal-based oxidation catalyst in (3) above; (5) Compensating for the shortage of NO ₂ generation at low temperature of the NOx oxidation catalyst by switching the injection timing of the engine to a state in which NO ₂ increase is generated; (6) NOx
A heater heating means is added to the oxidation catalyst to reduce NO ₂
Compensate for the shortage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the treatment of exhaust gas from a diesel engine, and more particularly to the prevention of clogging of a particulate filter for diesel engine exhaust gas or the regeneration of the filter (including a partial cleaning process). A method and an apparatus therefor.

[0002]

2. Description of the Related Art A filter (DP) is used to filter and remove particulates in exhaust gas from a diesel engine.
F: Diesel Particulate Filter
r) has been installed and used in exhaust pipe systems. The particulates are mainly derived from the fuel, soot, organic solvent-soluble organic substances (SO
F: Solubleorganicfraction)
And the like. Examples of filters for trapping and removing such particulates from exhaust gas include a wire mesh packed layer of a heat-resistant or fire-resistant material; a monolithic multi-tube having a breathable microporous partition made of a refractory material, for example, cordierite. Structure; metal skeleton (skeleton) or foam structure (eg, open cell structure such as Raney nickel). The monolithic multi-tube structure has a tube portion (A) having an upstream end opened and a downstream end closed, and a tube (B) having an upstream end closed and a downstream end opened. Is a monolithic structure in which a large number of both are generally arranged alternately and bundled in a monolithic manner. The partition wall between the pipe portions (A) and (B) has a thickness of, for example, 1 mm.
To the extent that they are microporous so that gas can pass through the partition. Exhaust gas enters from the upstream opening of the pipe (A), passes through the microporous partition wall, moves into the pipe (B), and flows out from the downstream opening end.
At that time, the particulates are substantially trapped by the microporous partition and are removed from the exhaust gas. However, when such particulate capture continues for a long period of time, a problem arises that the deposition of particulates causes clogging of the microporous partition wall (filter) and prevents normal exhaust gas emission. . Such a clogging phenomenon similarly occurs at a gap between meshes when a wire mesh packed bed filter is employed, and at a pore in a skeletal structure filter. Therefore, preventing such clogging or regenerating or at least partially cleaning the clogging or clogged filter in a timely, fast and efficient manner is always good and necessary. The filtration performance must be maintained to ensure smooth flow of exhaust gas and discharge. Conventionally proposed DPF cleaning means include:
The filter body is equipped with an electric resistance heating wire, and when it is contaminated with carbonaceous deposits, it is energized to heat the filter, thereby burning off the carbonaceous deposits. (Example: air) Backwash with a stream to remove and remove carbonaceous deposits for cleaning,
In addition, there is a method in which the gas flow containing the carbonaceous material particles removed at that time is brought to a combustion condition in another place, and the carbonaceous material is burned and removed. Not practical. U.S. Pat. No. 4,902,487 discloses that particulate matter captured on a filter is contacted with NO ₂ gas as an oxidizing agent at a temperature of 400 ° C. or less to burn the captured particulate (oxidation). ) And carbon oxides (CO ₂ ,
It is described to be removed as CO), and NO ₂ acting as an oxidizing agent is obtained by converting NO in exhaust gas to NO ₂ by the action of a platinum group metal catalyst disposed upstream of the filter. Is also shown. JP-A-63-51947 discloses that a highly heat-conductive metal plating (Cu or Ag) is formed on a filter made of a refractory three-dimensional structure or a carrier having an inorganic oxide film further coated thereon. And a catalyst filter for particulate combustion in which a catalyst plating layer of at least one noble metal of Pt, Pd, Rh is formed thereon.
Japanese Patent Application Laid-Open No. Hei 3-213146 discloses a heat-resistant porous foam type exhaust gas purifying filter, which is composed of a relatively low-density part at the entrance side where particulates can easily enter and a high-density thin layer at the exit side. And Cs; Cu; or Ce / L throughout.
(a) discloses a filter that carries at least one catalyst component of (a) to burn particulates and reduce NOx, and emphasizes a synergistic effect caused by the coexistence of an alkali metal, a transition metal, and a rare earth element with the particulates. ing.

[0003]

SUMMARY OF THE INVENTION The present inventors have proposed a DPF
The present invention has been completed by earnestly studying and examining the practical cleaning means. That is, the present invention can efficiently purify a filter used for filtering and removing particulates contained in a diesel engine exhaust gas over the entire operating condition range of the diesel engine, and the filter by the accumulation of the particulates can be used. A practical means and apparatus for easily preventing harmful clogging, ensuring effective removal of particulates, and constantly maintaining good filtration characteristics that do not hinder engine operation. Its main purpose is to.

[0004]

According to a first aspect of the present invention, in an exhaust gas recirculation (EGR) type diesel engine for returning a part of exhaust gas to an intake pipe, an intake control valve is provided in an intake pipe system. The exhaust pipe system includes one or more of an exhaust gas recirculation passage, an exhaust control valve, a reducing agent supply system, a NOx storage reduction catalyst, and a DPF (diesel) for filtering and removing particulates in exhaust gas. (1) NO is mainly oxidized into NO ₂ by the NOx storage reduction catalyst during the operation in the normal lean state and occluded by the catalyst, and the operation in the lean state is further performed. continuing beyond the storage capacity of the NOx storage reduction catalyst is occluded by it so as to produce a breakthrough NO ₂ a, DPF on with its breakthrough NO ₂ downstream to act as an oxidizing agent When the trapped particulates are oxidized and removed and the desired DPF cleaning is achieved, the operation in the lean state is terminated. (2) Then, the intake control valve, EGR, exhaust control valve, and the introduction of the reducing agent switched to the rich-state operation by one or more of the means of the inner, already NO ₂ stored in the NOx storage catalyst and reduced and removed to regenerate the NOx storage-reduction catalyst by doing so, the playback is completed Sometimes, the cycle of (1) returning to the DPF cleaning due to NO ₂ breakthrough and the operation continuation under the lean state is repeated, and then the cycle of (2) regenerating the NOx reduction storage catalyst under the rich state is repeated. NOx storage reduction catalyst juxtaposition type D
Provided is a PF cleaning device. N in the above (1)
The time required for cleaning due to O ₂ breakthrough is on the order of several tens of seconds, for example, about 30 to 60 seconds, and the time required for catalyst regeneration under the rich condition (2) is, for example, 5 seconds or less. Short time is enough. Conventionally, it is known to use a NOx storage reduction catalyst for purifying diesel engine exhaust gas. Such catalysts are, for example,
Platinum (oxidation catalyst component) and barium (occlusion agent component) are supported on a carrier made of alumina. During operation in the lean state, NOx in the exhaust gas is oxidized in the form of NO ₂ in contact with the catalyst, and are inserted therein. The chemical process that takes place is typically NO + O ₂
Represented by ⇒NO _2. Conventionally, when the limit of the storage capacity of the catalyst is near (it can be detected by the NOx sensor).
Then, breakthrough of the storage catalyst by NO ₂ (breakthro
For the purpose of preventing the occurrence of the low state (high), switching from the lean state to the rich state has been performed. By this switching, reducing substances (eg, hydrocarbons, reducing agents, carbon monoxide, etc.) are present in the exhaust gas, and the stored NO
₂ is reduced to N ₂ by the action of the reducing substance and released from the storage catalyst, and thus the storage capacity of the storage catalyst is restored (that is, the storage catalyst is regenerated). As an example of the reaction in this case, for example, NO ₂ + HC + CO → N ₂ + CO ₂
+ H ₂ O, where HC (hydrocarbon)
And CO (carbon monoxide) are reducing substances. In the present invention, unlike the above-described prior art in which the NOx storage catalyst is regenerated before the breakthrough of the NOx storage catalyst due to NO ₂ occurs, the regeneration timing of the storage catalyst is intentionally delayed. By the way, N
O ₂ allows the storage catalyst to break through over a period of time. The NO _{2 that} has passed through the storage catalyst acts as an oxidizing agent on the particulates (carbonaceous substance; C) captured by the DPF, for example, NO ₂ + C (particulates)
⇒ The deposition particulates are oxidized and removed by a reaction such as N ₂ + CO ₂ , and thus DPF cleaning can be conveniently achieved by continuing such NO ₂ breakthrough state for a while. Once the desired degree of cleaning of the DPF has been achieved, operation is switched to normal lean operation.
The degree of completion of the cleaning of the DPF can be mainly detected, for example, by monitoring with a NOx sensor installed downstream of the DPF. In this case, the control NOx sensor can be added in place to more accurately monitor the degree of completion of the cleaning. The most important feature of the above aspect of the present invention is the NO.
_{The second point is that} the storage catalyst breakthrough is effectively used for cleaning and regenerating the contaminated DPF. A specific example of the apparatus according to the first aspect of the present invention will be described with reference to FIG. FIG.
In the device shown in (1), the exhaust pipe 2 extends from the diesel engine 1 through the manifold, and the EGR pipe 3 branches off along the way to return to the intake pipe 16 of the engine to form an EGR passage. The EGR pipe includes an EGR control valve 4 on the way. An intake pipe 16 from the air cleaner 17 to the engine is located upstream of the EGR return position.
It has. After branching off the EGR pipe, the exhaust pipe further extends and is provided with an exhaust control valve 6 and a reducing agent supply pipe 13 in the middle thereof, and then a temperature sensor 10, and a NOx storage reduction catalyst 8 and a DPF 9 downstream thereof. Has built-in. A NOx sensor 11 is provided downstream of the DPF. The exhaust pipe is finally provided with a muffler muffler. The reducing agent supply pipe 13 is supplied with a reducing agent (for example, light oil) from a reducing agent tank via the pump 7. The engine is provided with a rotation sensor 14 and a load sensor 15, and sends detection data to the computer 12. The temperature sensor 10 and the NOx sensor 11 also send detection data to the computer 12. The computer operates any one of the intake control valve 5, the EGR control valve 4, the exhaust control valve 6, and the reducing agent supply pump 7 alone or in an appropriate combination on the basis of these input data to obtain a necessary lean state or rich state. And the appropriate temperature conditions for catalyst regeneration are created. In the above device, the diesel engine 1
NOx and particulates discharged from the exhaust pipe 2
, NOx is stored in the NOx storage reduction catalyst 8, and particulates are captured by the DPF 9. In the NOx storage reduction catalyst 8, NOx, for example, NO mainly contains NO ₂
It is oxidized to but are inserted, beyond the vicinity of the occlusion limit, or it is discharged into the catalyst outlet in the form of NO ₂ (NO ₂
Breakthrough), oxidize and purify the particulates trapped on the DPF. On the other hand, the presence of stored NOx on the NOx storage catalyst 8 is estimated by a NOx sensor, and after checking that the temperature at the catalyst inlet is appropriate, a rich state is formed to regenerate the NOx storage catalyst 8. At this time, smoke (particulates) is discharged from the engine.
It is trapped by PF9, which is oxidized and purified in a timely manner as described above, so that there is no inconvenience.

FIG. 2 shows the air-fuel ratio (λ) (upper stage) in the lean state and the rich state observed in the implementation of the apparatus according to the first embodiment of the present invention, and N at the outlet side of the NOx storage reduction catalyst.
The change of the Ox (NO ₂ ) concentration (lower) with respect to time is shown by a pattern diagram. Normally operating in a lean state with a λ value exceeding about 2, NO ₂
Breakthrough increases and its action as an oxidizing agent causes DP
The cleaning of F is performed quickly and without requiring a very high temperature, and then the air-fuel ratio value is switched to a rich state (λ <1).
The NOx storage reduction catalyst is saturated reduction playback NO _2. As described above, the continuation of the rich state is sufficient in a short time on the order of several seconds.

In the first embodiment shown in FIG. 1, the recirculation passage for recirculating a part of the exhaust gas comprises a catalyst and a DPF.
Has an exhaust gas inlet provided on the upstream side of
Such an exhaust gas inlet may be provided downstream of the DPF, and a similar DPF cleaning effect can be achieved.

According to a second aspect of the present invention, trapped particulates are oxidized and burned in a filter (DPF) provided in an exhaust pipe system for filtering and removing particulates in exhaust gas from a diesel engine. A DPF cleaning apparatus carrying a catalyst, wherein the catalyst includes any of silver; copper and its oxide; and a combination of silver, copper and its oxide and ceria. Is done. The catalyst may be composed of platinum or a combination of platinum, silver, copper and ceria.

The cleaning device according to the second aspect of the present invention is, for example, a DPF in the form of a monolithic multitubular structure having a gas-permeable microporous partition wall made of cordierite as described above.
Can be prepared by a generally known dip coating method of dipping in an aqueous slurry containing a catalytic metal compound and a binder, withdrawing, drying and baking. The starting catalytic metal compound is preferably water-soluble. For example, silver nitrate (AgNO ₃ ), copper nitrate [Cu (NO ₃ ) ₂ ], and the like. Ceria (cerium oxide) is used in the form of a fine powder. The binder is preferably alumina sol, silica sol, or the like, and those skilled in the art can easily select and adopt the binder.

[0009] Without loading a catalyst on the DPF of this embodiment,
Oxidation of trapped particulates generally requires temperatures of about 600 ° C. or higher, but such high temperatures are unlikely to occur under normal diesel engine operating conditions, and should not exceed full load. Area only. Thus, unless the DPF is heated to such a high temperature, for example by electric heating means, or the temperature of the exhaust gas is rarely such a high temperature, the trapped particulates are the DP particulates.
It cannot be removed from F. However, in the catalyst-supported DPF of this aspect of the present invention, the combustion start temperature of particulates is significantly reduced, and is approximately 400 to 450 ° C., which substantially coincides with the range that often occurs as the exhaust gas temperature under normal operating conditions of a diesel engine. Was found to be. For example, in an experimental example, a silver-loaded DPF
Is about 450 ° C. for particulates, and about 430 ° C. for copper-supported DPF,
It was observed that the combustion start temperature was about 400 ° C. in the copper / ceria-supported DPF, and it was found that the DPF could be self-cleaned in a considerably wide temperature range from a medium load range to a full load range. The result is shown graphically in FIG. FIG. 8 also shows the results when unsupported DPF was used for comparison, and the “baseline” in the figure means the combustion start temperature in unsupported DPF, This value is generally in the range of approximately 550 ° C to 600 ° C.

[0010] Thus, the DPF cleaning apparatus carrying the special catalyst according to the second aspect of the present invention covers a substantial part of the exhaust gas temperature range under the normal operating conditions of the diesel engine with respect to the self-cleaning of the DPF. Can be. However, the cleaning device of this embodiment may extend the DPF cleaning temperature range (especially to a lower temperature side) by supplementarily using the above-mentioned cleaning by known electric heating means and backwashing cleaning by a gas flow, if necessary. , Its practicality can be enhanced. Even if a cleaning device using electric heating means is additionally provided, the opportunity and time for the operation of electric heating cleaning are small, and the power consumption for the operation is small. Also, in the case of using a method of backwashing the DPF contaminated or clogged by particulate capture with a gas flow, the frequency of the backwash operation can be significantly reduced.

In a third aspect of the present invention, a noble metal-based oxidation catalyst is provided upstream of the DPF, and some components in the composition of the exhaust gas, for example, NOx and SOF (organic solvent-soluble organic substance) are previously determined. This is a DPF cleaning apparatus of a type in which exhaust gas flows into the DPF after denaturation. The device according to the third aspect is an exhaust gas recirculation (EGR) type diesel engine that returns a part of the exhaust gas to an intake pipe, and includes an intake control valve in an intake pipe system; A passage, an exhaust control valve, a noble metal oxidation catalyst, and a DPF (Diesel Particulate Filter) for filtering and removing particulates in the exhaust gas are provided in series; By controlling at least one of the amount of exhaust gas by the valve and the amount of recirculated exhaust gas by EGR, the temperature of the noble metal-based oxidation catalyst and the exhaust gas flowing into the DPF is controlled to prevent particulate accumulation on the DPF, or A DPF cleaner characterized by forming conditions of an appropriate oxidizing atmosphere to prevent clogging of the DPF. It is a packaging apparatus.

Before describing the third embodiment of the present invention, DP
An outline of the action of the oxidation catalyst on particulates in various ranges of temperature of the exhaust gas under the normal conditions of a diesel engine when treating the exhaust gas by combining and arranging the oxidation catalyst upstream of F will be described. . (1) About 10
In the temperature range of 0 to 250 ° C., the soot component in the particulates goes to the DPF without burning even in contact with the oxidation catalyst, and is captured there. Organic solvent-soluble organic substances (SOFs) in the particulates are partially burned and reduced by the oxidation catalyst. Therefore, in this temperature range, most of the particulate goes to the downstream DPF and is trapped there. (2) About 250-45
In the temperature range of 0 ° C., NOx (eg, N
O) is oxidized to NO ₂ by the oxidation catalyst (for example,
NO + O ₂ ⇒NO ₂ ). This NO ₂ acts as an oxidizing agent,
The particulates (mainly soot components) deposited on the DPF are burned, thereby cleaning and regenerating the DPF (for example, NO ₂ + C → N ₂ + CO ₂ ).
In this temperature range, SOF is well oxidized and reduced. (3) In the temperature range of about 450 to 550 ° C., the above-mentioned NOx oxidation reaction turns from equilibrium to the opposite direction, and the production of NO ₂ useful as an oxidizing agent for DPF cleaning decreases, or NO ₂ is reduced. It returns to NOx (for example, NO). Thus, in this way, soot combustion starts to decrease gradually in the absence or absence of the oxidant, and the DPF
Above particulates cannot be removed. (4) In a temperature range exceeding about 550 ° C., the particulates self-burn, so that the DPF can self-regenerate. The present inventors have determined that the step of depositing particulates on the DPF occurs, that is, the above-mentioned temperature range of about 100 to 250 ° C. (1); and that the burning and removal of the particulates deposited on the DPF is stopped or reduced. Attention is paid to the existence of the above-mentioned temperature range (3) of about 450 to 550 ° C., and the temperature of the exhaust gas is controlled so as not to cause the phenomenon appearing in these two temperature ranges. The idea was to shift to the temperature range of (2) in the case of the temperature range of (1) and shift to the temperature range of (4) in the case of the temperature range of (3).

Therefore, the third aspect of the present invention relates to (1) about 100 to 250 ° C. and (3) about 450 to 5 ° C.
In both temperature ranges of 50 ° C., in view of the fact that particulates accumulate on the DPF or that particulates deposited on the DPF are not burned off, when the temperature of the exhaust gas is in both these ranges, control valve, with at least one means of the exhaust control valve and EGR, to a temperature range on each one stage [Sunawachi, (1) from (2) NO ₂ oxidant to generate phase;
From (3) to the self-combustion stage of (4)] By increasing the exhaust gas temperature, the particulates do not deposit on the DPF, and the particulates deposited on the DPF are burned off. Things. Regarding the individual actions of the exhaust gas temperature control means in this embodiment,
Although not described, EGR increases the concentration of hydrocarbons (HC) in the exhaust gas; decreases the amount of exhaust gas by the intake control valve and / or the exhaust control valve; and generates heat in the oxidation reaction by the catalyst. At least one is appropriately used in the present invention. The operation of these temperature control means can be performed by a computer. In this embodiment, in some cases, even if the oxidation catalyst is omitted, the required necessary temperature control can be performed by appropriate application of the EGR and the intake control valve / exhaust control valve. This is a modification of the third embodiment of the present invention.

FIG. 3 is a schematic diagram of an example of a specific device according to the third aspect of the present invention. In the device shown in FIG.
An exhaust pipe 2 extends from the diesel engine 1 via a manifold, and an EGR pipe 3 branches off along the way to return to an intake pipe 16 of the engine to form an EGR passage. The EGR pipe includes an EGR control valve 4 on the way. An intake pipe 16 extending from the air cleaner 17 to the engine includes an intake control valve 5 upstream of the EGR return position. EG
After branching off the R pipe, the exhaust pipe further extends, and is provided with an exhaust control valve 6 and a temperature sensor 10 in the middle thereof, and the cross-sectional area thereof is increased downstream of them to remove the noble metal-based oxidation catalyst 8 and the DPF 9. A muffler (not shown) is provided at the end. The detection data of the temperature sensor 10 that detects the temperature of the exhaust gas is sent to the computer 12. The computer sends an output signal for operating at least one of the EGR control valve 4, the intake control valve 5, and the exhaust control valve 6, or an appropriate combination according to the temperature value, and outputs the temperature as described above. Range 1 (about 1
00 to 250 ° C.) to temperature range 2 (about 250 to 450
C: Shift to DPF purification stage by oxidation) and shift from temperature range 3 (about 450-550 ° C) to temperature range 4 (self-combustion stage). An example of a flowchart of computer control based on exhaust gas temperature data is illustrated in FIG. 9 for reference. The temperature values in the figure are examples,
Not a limiting value.

[0015] In another preferred embodiment of this third aspect, upstream of the oxidation catalyst and DPF, DP
A pressure sensor is provided to detect the degree of clogging of F or the degree of contamination thereof, and the detection data is sent to the computer 12 so that the exhaust gas pressure in the exhaust pipe is lower than the atmospheric pressure by a predetermined allowable range. Predetermined value, for example, 200 m
When it is detected that the pressure exceeds mHg, at least one of the EGR control valve, the intake control valve and the exhaust control valve, or an appropriate combination thereof may be operated to perform the exhaust gas temperature shift. FIG. 10 shows an example of a flowchart in the case of computer control based on the above pressure data for reference. The pressure values in the figures are illustrative and not limiting.

In such a specific example, as a criterion for performing the DPF cleaning operation, a pressure parameter in addition to the temperature parameter of the exhaust gas may be adopted, and the cleaning operation is performed until a predetermined exhaust gas pressure is detected. If control to postpone the start of implementation is performed, generally DP
There is a practical advantage that the frequency of F cleaning is reduced. In these cases, the completion point of the DPF cleaning operation is determined based on the pressure value data from the pressure sensor, and an operation stop signal is output from the computer.

The oxidation catalyst used in the third embodiment of the present invention is a noble metal such as platinum (Pt), palladium (P
d) is supported on a carrier, for example, alumina. In practice, a water-soluble noble metal compound, alumina Z powder and a binder (for example, alumina sol, silica sol) are homogeneously mixed with water to form an aqueous slurry. It can be manufactured by a known dip coating method in which a honeycomb carrier (for example, made of cordierite) is dipped, pulled up, dried, and fired.

The description of the first to third aspects of the present invention is based on the description that the catalyst (NO) is used to guide a part of the exhaust gas to the recirculation passage.
x storage catalyst or oxidation catalyst) or when introduced from the upstream side of the DPF. In any of these embodiments, the exhaust gas recirculation introduction port may be provided downstream of the DPF (see FIG. 4). ), It was confirmed that the objects and effects of the present invention were equally achieved. Therefore, providing the exhaust gas inlet of the exhaust gas recirculation passage downstream of the DPF is also within the scope of the present invention. FIG. 4 is an enlarged view of the DPF installation portion of the exhaust pipe system, and shows a case where an exhaust gas inlet to the EGR pipe 3 is provided downstream of the DPF 9.

In any of the above aspects of the invention,
Attach rotation sensors and load sensors to the diesel engine, input information from them to a computer,
It is possible to improve the accuracy of the control output for operating the F cleaning device.

The present invention further relates to another NO ₂ regeneration type DPF.
A cleaning device is also provided. That is, a NOx oxidation catalyst and a NO ₂ regeneration type DPF (diesel particulate filter) are arranged in series in an exhaust pipe system from a diesel engine.
A diesel engine DPF cleaning device for removing trapped and deposited particulates on a DPF by oxidative combustion by oxidizing power of NO ₂ generated from Ox,
(A) means for detecting excessive accumulation of particulates in the DPF above a predetermined amount based on a back pressure rise value measured by a pressure sensor disposed before and after the DPF; (b) temperature of exhaust gas, NOx concentration, etc. sensor means for detecting the state; (c) is input to the detection signal of the (i) and (ii) means, temporarily NOx to be NO ₂ required to remove the excess particulates accumulated on the DPF In order to temporarily increase the fuel injection timing to the diesel engine or to delay the timing in order to temporarily generate, in the exhaust gas, conditions such as temperature suitable for oxidative combustion removal of the excessively accumulated particulates. To the fuel injection pump, and as a result of this timing displacement fuel injection, Electronics for outputting a command signal for returning the fuel injection timing to the normal position to the fuel injection pump by judging from the detection signal from the pressure sensor means (a) the time when the fuel injection is completed or completed to a desired degree. The DPF cleaning apparatus according to the above, further comprising processor means. By including the oxidation catalyst in the DPF itself in this aspect, it is possible to promote the oxidative combustion of the deposited particulates and improve the removal effect thereof.

An example of the above-mentioned NO ₂ regeneration type DPF cleaning apparatus is schematically shown in FIG. Diesel engine 5
The exhaust gas discharged from 1 is exhaust manifold 52,
It passes through the exhaust pipe 53 and is introduced into the subsequent DPF cleaning device main body 54. The inside of the DPF cleaning device main body 54 has a structure in which a NOx oxidation catalyst 61 is arranged on the upstream side and a DPF 62 which is a particulate collection device is arranged on the downstream side. When the exhaust gas is introduced into the DPF cleaning device, it first passes through the NOx oxidation catalyst 61, and particulates are collected by the DPF 62, and other components are discharged to the outside through an exhaust pipe. At this time, the exhaust gas temperature becomes approximately 20
In the range of 0 to 450 ° C., the NOx catalyst works effectively and NOx (mainly NO) in the exhaust gas is oxidized to NO ₂ having a strong oxidizing power. The particulates collected and accumulated in the DPF can be burned and removed by using the strong oxidizing NO ₂ .

In the present invention, in order to completely and stably remove particulates by oxidizing and burning with NO ₂ , various sensors are used to detect the state of collection and accumulation of particulates in the DPF 62 and the state of regeneration of the DPF. When necessary (for example, when excessive particulates accumulate in the DPF, or when such a state is occurring), the operating state of the engine (mainly the fuel injection timing) is controlled to regenerate the DPF. Or DPF
To prevent further accumulation of particulates on
It optimizes the temperature range of the exhaust gas, the promotion of NO ₂ generation, and the prevention of particulate generation. The balance between the amount of particulates collected and the amount of particulates oxidized and burned off in the DPF cleaning device main body 54 is lost, and the DPF
When the particulate deposition on 62 begins to increase, D
The pressure sensors 59 disposed before and after the PF detect an increase in the back pressure, and the back pressure (rise) value signal is output from the ECU / EDU5.
5 and the data signals for grasping and monitoring other driving conditions are also provided by a rotation sensor 56, an accelerator (load) sensor 57, a NOx sensor 58, and a temperature sensor 6.
0 is input to the ECU / EDU 55 (see FIG. 5). Based on these data, optimization of the exhaust gas temperature (preferably about 300 to 400
(In the range of ° C.) and the injection timing of the fuel injection pump 63 is changed (mainly advanced) to promote the generation of NO _2.
To send a signal.

When the particulates accumulated in the DPF start burning under the above control, the pressure sensor 59 and the temperature sensor 60 detect a rise in the temperature of the exhaust gas and a decrease in the back pressure due to the burning of the particulates. ECU / ED
This cycle is repeated until U55 determines the regeneration status of the DPF 62, controls the engine again if necessary, and determines that particulate removal by the DPF has been completed. FIG. 6 shows a block diagram of the input / output of the ECU / EDU control. This figure shows detection data signal inputs from various sensors 6 to 9 and an instruction signal output to the fuel injection pump after analyzing the data.

In the conventional NO ₂ regeneration type DPF cleaning apparatus, as described above, NOx in exhaust gas is oxidized to NO ₂ having strong oxidizing power using a catalyst in a rather limited temperature range, and the generated NO ₂ Is used to regenerate the DPF by burning and removing soot (particulates) collected and accumulated in the DPF. Also referred to as a continuous regeneration trap, the required generation of NO ₂ depends on the exhaust gas temperature. Therefore, for example, in a low temperature range up to about 200 ° C., NOx → N
Since the conversion of O ₂ is suppressed, the particulates are not removed, and the collection of the particulates in the DPF continues, the amount of the particulates deposited on the DPF gradually increases for a certain period of time, and the DPF becomes clogged. Occurs, where an excessive increase in back pressure occurs, which may cause a decrease in engine operating performance.

In contrast to the disadvantages of the prior art described above,
In the DPF cleaning apparatus of the present invention shown in FIGS. 5 and 6, when the exhaust gas temperature is in a low temperature range and the accumulation of particulates in the DPF is expected, the operating state of the engine is changed (mainly by fuel injection). Since the control is performed so as to generate exhaust gas conditions suitable for removing particulates (by displacing the timing in the advance direction or in the direction that delays the timing), it is possible to effectively increase the amount of particulate accumulated on the DPF over time. Therefore, maintenance-free and stable DPF performance can be maintained for a long period of time.

The present invention relates to a NO_TwoRegeneration type D
A PF cleaning device is also provided. That is, Dize
Heating fuel into the exhaust system from the
Means for supplying; burning supplied fuel to obtain high temperature
NOx with high oxidizing power _TwoOxidation catalyst to be converted to
For filtering and removing particulates_TwoPlayback
Type DPF (diesel particulate filter);
In a DPF cleaning device arranged in series,
The oxidation catalyst is provided with a heater heating means so that the
Temperature is NOx of NOx in the oxidation catalyst_TwoFor conversion to
The amount of NO that is too low for DPF cleaning_Two
If no acid is generated, the heater heating means is activated to
The temperature of the catalyst for_TwoGenerate DP
Remove particulate matter deposited on F as required
And the engine is turned on during these operations.
From speed sensors, load sensors and exhaust gas temperature sensors
Input data signals and heating based on them
ON / OFF of fuel supply and adjustment of supply amount, and
ON / OFF of heater heating and control of its heating intensity
It is equipped with a computer that outputs control signals
The above DPF cleaning device. With this device
Is the heater before the particulate reaches the DPF
Control heater heating so that it is burned off by heating
Can also. Oxidation of particulates in the DPF itself
Oxidation catalysts that promote combustion can also be included.
DPF cleaning effect by the addition of catalyst
It can be further improved.

FIG. 7 schematically shows an embodiment of the DPF cleaning apparatus of the heating fuel supply / heater heating type.
A fuel supply pump 105 and a fuel supply nozzle 113 are attached as means for supplying a heating fuel (generally, hydrocarbons such as light oil) to an exhaust pipe 102 from the diesel engine 101, and a heater heating means is provided downstream thereof. Catalyst 10
7 and a DPF 108, and a muffler 109 is further mounted. Data signals detected by the rotation sensor 103 and the load sensor 104 attached to the engine and the temperature sensor 114 attached to the exhaust pipe are input to the computer 111. Based on these input data, the computer 111 issues an operation instruction signal to the fuel supply pump 105 when it is determined that fuel supply for heating is necessary, and also supplies a catalyst 107 with heater and a power supply (battery) for current supply for its operation. Controller 112 connected to
Also issues an instruction signal. This control is performed on / off of heating fuel supply and its supply amount, and on / off and heating intensity of heater heating. The heater-equipped catalyst 107 is composed of, for example, a body in which a stainless sheet is coiled, and has a surface coated with an oxidation catalyst and provided with a heating wire. The DPF 108 may be made of, for example, cordierite or SiC
Filter. In the DPF cleaning apparatus according to this aspect of the present invention, the DPF trapping particulates can be burned and removed even in a region where the temperature of the exhaust gas is low, and clogging of the DPF can be effectively prevented.
As a result, good performance of the DPF can be maintained for a long period of time.

[Brief description of the drawings]

FIG. 1 is a schematic view of a DPF cleaning apparatus according to a first embodiment of the present invention.

FIG. 2 is a time-dependent pattern diagram of the lean and rich states of the apparatus of FIG. 1 and the NOx concentration at the NOx storage reduction catalyst outlet side.

FIG. 3 is a schematic diagram of a DPF cleaning apparatus according to a third embodiment of the present invention.

FIG. 4 is a partially enlarged view showing an exhaust gas introduction port to an EGR pipe provided downstream of the DPF.

FIG. 5 is a schematic view of one embodiment of an NO ₂ regeneration type DPF cleaning apparatus according to the present invention.

FIG. 6 is an ECU / EDU input / output flowchart for controlling the apparatus of FIG. 5;

FIG. 7 is a schematic view of another embodiment of the NO ₂ regeneration type DPF cleaning apparatus according to the present invention.

FIG. 8 is a graph showing the particulate combustion start temperatures of various catalyst-supported DPFs in comparison with the values of unsupported DPFs.

FIG. 9 is an example of a flowchart of computer control of DPF cleaning based on exhaust gas temperature data.

FIG. 10 is an example of a flowchart of computer control of DPF cleaning based on exhaust gas pressure data.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Diesel engine 2 Exhaust pipe 3 EGR pipe 4 EGR control valve 5 Intake control valve 6 Exhaust control valve 7 Reducing agent supply pump 8 NOx storage reduction catalyst (or noble metal-based oxidation catalyst) 9 DPF 10 Temperature sensor 11 NOx sensor 12 Computer 16 Intake Pipe 17 Air cleaner 51 Diesel engine 52 Exhaust manifold 53 Exhaust pipe 54 DPF cleaning device main body 55 ECU / EDU 56 Rotation sensor 57 Accelerator (load) sensor 58 NOx sensor 59 Pressure sensor 60 Temperature sensor 61 NOx oxidation catalyst 62 DPF 63 Fuel injection pump 101 Diesel engine 102 Exhaust pipe 103 Rotation sensor 104 Load sensor 105 Heating fuel supply pump 106 Fuel (light oil) tank 107 Heater (possibly with catalyst) 1 8 DPF 109 muffler 110 heater power supply (battery) 111 Computer 112 controller 113 for heating the fuel supply nozzle 114 temperature sensor

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) F01N 3/02 321 F01N 3/08 B 4D048 3/08 3/10 A 3/10 3/20 B 3/20 3 / 28 301C 3/28 301 3/36 B 3/36 F02D 41/04 360A F02D 41/04 360 385Z 385 41/14 310N 41/14 310 41/40 D 41/40 43/00 301H 43/00 301 301K 301N 301T B01D 53/36 102H 104A (72) Inventor Hironobu Mogi 3-1-1, Hinodai, Hino-shi, Tokyo Fino term in the Hino Plant of Hino Motors, Ltd. 3G084 AA01 AA03 BA05 BA09 BA13 BA19 BA20 BA24 BA26 DA10 DA27 EA11 EB01 FA10 FA18 FA27 FA28 FA33 3G090 AA03 BA04 CA01 CA02 CB04 CB11 DA04 DA12 DA18 DA20 EA02 EA06 EA07 3G091 AA02 AA11 AA18 AA28 AB02 AB06 AB09 AB13 BA01 BA04 BA14 BA33 CA03 CA13 CA18 CB02 DA03 CB02 DA07 CB02 DA08 EA33 FB10 FB12 FB15 FB16 FC02 FC04 FC06 G A06 GB01W GB05W GB10W HA08 HA09 HA14 HA15 HA18 HA36 HA37 HA38 HA42 HA47 HB03 HB05 3G301 HA02 HA04 HA06 HA13 HA15 JA15 JA24 JA25 JA26 JA33 JB09 LA03 LB11 MA01 MA11 MA18 NA06 NA07 NA08 NE01 NE06 NE13 NE14 NE15 PA17B01ZPD01 PE03Z PF03B PF03Z 4D019 AA01 BA01 BA02 BA06 BA07 BB06 BC07 CA01 CB04 CB09 4D048 AA14 AB01 AC02 BA10X BA19X BA30X BA34X BA35X BA41X BB02 BD04 CA01 CC27 CC32 CC38 CC53 CD05 CD08 DA01 DA02 DA06 DA07 DA10

Claims (10)

[Claims] An exhaust gas returning part of the exhaust gas to an intake pipe.
In a recirculation (EGR) diesel engine,
Equipped with air intake control valve in tracheal system; exhaust gas in exhaust system
One of the circulation passage, exhaust control valve, and reducing agent supply system
Or multiple catalysts, NOx storage reduction catalyst,
DPF (diesel pump)
(1) a normal filter is provided in series;
During operation in the lean state, the NOx storage reduction catalyst
O mainly NO_TwoAnd oxidize it into the form of
The operation in this lean state is continued, and NOx is absorbed.
NO by storing more than the storage capacity of the storage reduction catalyst_TwoBreakthrough of
And the breakthrough NO_TwoOxidizer
Patiki captured on DPF downstream
Oxidized and removed to achieve the desired DPF cleaning
At the time of completion, operation in this lean state ends,
(2) Next, the intake control valve, EGR, exhaust control valve
By one or more of the following methods:
To a rich operation state,
NO stored in the NOx storage catalyst _TwoTo reduce and remove
To regenerate the NOx storage catalyst and complete the regeneration
Then, (1) the continuation of the operation under the lean state and N
O_TwoReturn to breakthrough DPF cleaning, then
The regeneration of the NOx storage reduction catalyst under the rich condition of (2) is performed.
NOx storage / return characterized by repeating a cycle
DPF cleaning device with co-catalyst. 2. A DPF cleaning apparatus in which a filter (DPF) provided in an exhaust pipe system for filtering and removing particulates in exhaust gas from a diesel engine carries a catalyst for oxidizing and burning trapped particulates. , Wherein the catalyst comprises any of silver; copper and their oxides; and a combination of silver, copper and their oxides and ceria. 3. An exhaust gas recirculation (EGR) type diesel engine for returning a part of exhaust gas to an intake pipe is provided with an intake control valve in an intake pipe system; an exhaust gas recirculation passage in the exhaust pipe system; Control valve, noble metal oxidation catalyst, DPF for filtering and removing particulates in exhaust gas
(Diesel Particulate Filter) in series; during operation of the engine, at least one of the intake amount by the intake control valve, the exhaust gas amount by the exhaust control valve, and the recirculation gas amount by the EGR is adjusted, and A DPF cleaning apparatus characterized by controlling the temperature of an oxidation catalyst and exhaust gas flowing into a DPF to form appropriate oxidation conditions for preventing particulate deposition on the DPF or preventing DPF from being clogged by the particulate. 4. An exhaust gas recirculation (EGR) type diesel engine for returning a part of exhaust gas to an intake pipe, comprising an intake control valve in an intake pipe system; an exhaust gas recirculation passage in the exhaust pipe system; Valves and a DPF (Diesel Particulate Filter) for filtering and removing particulates in exhaust gas are provided in series; during operation of the engine, the amount of intake air by the intake control valve, the amount of exhaust gas by the exhaust control valve, and the replenishment by EGR. At least one adjustment of the amount of circulating gas is performed to control the temperature of the exhaust gas flowing into the DPF to prevent particulate accumulation on the DPF, or an appropriate oxidizing atmosphere condition to prevent clogging of the DPF due to the particulate. A DPF cleaning apparatus characterized by forming: 5. The DPF cleaning apparatus according to claim 4, wherein a pressure value of the exhaust gas flowing into the DPF is employed in addition to a temperature value of the exhaust gas flowing into the DPF as a criterion for performing the DPF cleaning. 6. The exhaust gas inlet of the exhaust gas recirculation passage is connected to D
The DPF cleaning device according to claim 1, which is provided downstream of the PF. 7. The catalyst according to claim 1, wherein the catalyst is platinum, silver, copper, and platinum.
3. The DPF cleaning apparatus according to claim 2, wherein the DPF cleaning apparatus includes one of a combination of silver, copper, and ceria. 8. An N pipe in an exhaust pipe system from a diesel engine.
An Ox oxidation catalyst and a NO ₂ regeneration type DPF (diesel particulate filter) are arranged in series, and the trapped and deposited particulates on the DPF are usually generated by the oxidizing power of NO ₂ generated from NOx by the action of the NOx oxidation catalyst. A diesel engine DPF cleaning device for removing oxidized combustion by oxidative combustion; (a) a back pressure increase value measured by a pressure sensor disposed in front of and behind the DPF to detect excessive accumulation of particulates in the DPF over a predetermined amount; (B) Sensor means for detecting the state of exhaust gas temperature, NOx concentration, etc .; (c) above (a) and (b)
Is inputted detection data signal means, for thereby temporarily increased generation of NOx as the NO ₂ required to remove the excess particulates accumulated on the DPF, and suitable for oxidative combustion removal of該過multi particulates accumulated A command signal is output to the fuel injection pump to set the fuel injection timing for the diesel engine to be advanced or retarded in order to temporarily generate conditions such as high temperature in the exhaust gas. A command signal for returning the fuel injection timing to the normal position is determined by judging from the detection signal from the pressure sensor means (a) a point in time when the removal of the excessively accumulated particulates is completed or completed to a desired degree as a result of the injection. Electronics processor means for outputting to the injection pump; Cleaning equipment. 9. means for supplying a fuel for heating as required into the exhaust pipe system of a diesel engine; oxidation to convert the NOx to give a high temperature by burning the supplied fuel to a high oxidative NO ₂ In a DPF cleaning apparatus in which a catalyst; and a NO ₂ regeneration type DPF (diesel particulate filter) for filtering and removing particulates are arranged in series, the oxidation catalyst is provided with a heater heating means, and a heater for heating the inflow exhaust gas is provided. Temperature is N of NOx in the oxidation catalyst.
If the conversion to O ₂ is too low to produce the required amount of NO ₂ for DPF cleaning, the heater heating means is activated to raise the temperature of the oxidation catalyst to reduce the required amount of NO ₂ . The generated and accumulated particulates on the DPF are removed to a required degree, and in these operations, data signals from an engine speed sensor, a load sensor, and an exhaust gas temperature sensor are input and input to them. The DPF cleaning apparatus according to claim 1, further comprising a computer which outputs a control signal for ON / OFF of heating fuel supply and adjustment of a supply amount thereof, and ON / OFF of heater heating and adjustment of heating intensity thereof. 10. The DPF cleaning apparatus according to claim 8, wherein the NO ₂ regeneration type DPF carries a catalyst that promotes the oxidative combustion of the particulates.